Carburetor construction to eliminate fuel accumulation at the reed valve

ABSTRACT

A uni-directional valve arrangement for two-cycle internal combustion engines which eliminates undesirable collection of pockets of fuel in the carburetor system and the resultant undesirable running characteristics, this being accomplished by venting from the mixing chamber of the carburetor system directly to the areas surrounding the unidirectional or &#39;&#39;&#39;&#39;reed&#39;&#39;&#39;&#39; valves so that an air fuel mixture moves through the restricted and dead pocket areas to keep them clean of fuel collections, thus preventing overrich comedown when a throttle is closed and preventing flooding under other running conditions.

United States Patent Schneider et a1. 1 1 Sept. 12, 1972 [54] CARBURETORCONSTRUCTION TO 1,600,007 9/1926 Mock ..261/D1G. 55 ELIMINATE FUELACCUMULATION 2,093,960 9/ 1937 Ericson ..261/D1G. 55 AT THE REED VALVE3,353,525 11/1967 Nutten et a1. ..123/73 X [7 Inventors: Kenneth C.Schneider; Chimes H. 3,361,120 1/ 1968 Schneider ..123/73 Tuckey, bothof Cass City, MlCh. Primary Examiner Mark M- Newman [73] Assignee:Walbro Corporation, Cass City, A i t E i -R B, Rmh

Mich. Attorney-Bames, Kisselle, Rajsch & Choate [22] Filed. Jan. 16,1970 ABSTRACT [21] Appl' 3437 A uni-directional valve arrangement fortwo-cycle internal combustion engines which eliminates undesira- U-S.Cl. v, A ble collection of of fuel in the carburetor ..F02b y tem andthe resultant undesirable running charac- [58] Field of Search ..123/73,73 V, 73 A, 74; teristics this being accomplished by venting from the261/DIG- 55; 137/513], 5133 mixing chamber of the carburetor systemdirectly to the areas surrounding the unidirectional or reed ReferencesC'ted valves so that an air fuel mixture moves through the UNITED STATESPATENTS restricted and dead pocket areas to keep them clean of fuelcollections, thus preventing overrich 1,788,358 1/1931 Goerg..1.37/513.7 comedown when a throttle is closed and preventing ward 1 13.7 under other running conditions 1,092,279 4/1914 Martin et a1...261/DIG. 55 1,585,142 5/1926 Gillett ..261/DIG. 55 1 Claim, 1 Drawingfigure CARBURETOR CONSTRUCTION TO ELIMINATE FUEL ACCUMULATION AT THEREED VALVE This invention relates to a Carburetor Construction toEliminate Fuel Accumulation at the Reed Valve and is particularlydirected to the use of a carburetor system with a two-cycle engine inwhich a unidirectional valve is provided at the entrance to thecrankcase of an engine to receive a fuel and air mixture from thecarburetor system of the engine.

In two-cycle engines, many efforts have been made to improve carburetionto prevent choking of the engine when the throttle is suddenly cut fromfull throttle to the idle range and also to prevent flooding when thereis a sudden change from the idle range to half or full throttle. Many ofthe problems have resulted from what is called puddling which means acollection of liquid fuel in certain areas of the engine. A change ofposition or a change in the running condition may cause the collectedfuel suddenly to enter the engine and cause flooding conditions.

The present invention has as its object the elimination of theseundesirable conditions of puddling and the provision of an extremelysimple revised structure which makes this possible. Many attempts havebeen made to solve this problem by complicated carburetion efforts andthe present system eliminates all of these requirements by a simplechange in the standard structures utilized in these engines.

Other objects and features of the invention will be apparent in thefollowing description and claims wherein the principles of operation ofthe invention are set forth together with the best mode presentlycontemplated for embodiment of such principles.

A drawing accompanies the disclosure and the single view therein shows across-section of a carburetor engine combination illustrating theinvention.

In the drawing, a carburetor structure is generally illustrated athaving a mixing passage 12 with a throttle valve 14 and a choke valve16. A diaphragm 18 controls a fuel inlet valve 20 of standardconstruction and fuel enters the mixing passage 12 through a main jet22. The idle passages of the system include a passage 24 leading to achamber 26 which has an idle port 28 at the throttle valve area of themixing passage.

The carburetor is attached to a two-cycle engine crankcase 40 wherein apiston 42 operates in a cylinder 44 with the usual piston rod 46 andcrankshaft 48. Interposed between the outlet end 50 of the mixingpassage 12 and the inlet end 52 of the engine is a mounting flange 54 ofa reed valve construction which is insulated from the metal housings byheat barriers 56 and 58. This is again standard construction. The reedvalve has a tapered valve cage 60 with openings 62 which are closed bythe flexible plates 64 commonly used in these reed valves. These platesare secured to the larger end of the tapered section by screws 66.

The invention lies in placing openings 70 in the flange 54 leading fromthe outlet of the mixing passage 12 to the pockets or corners 72 at thebase of the reed valve in the entrance to the passage 74 and the inletend 52. Thus, there is a venting of the so-called pockets or dead spacessurrounding the reed valve and this eliminates the so-called puddling ofliquid fuel which can happen during the idling stage of the engine.Someal ih li 5 i ti e ltiltfifi rlfi illi wage? the globs of fuel willbe carried into the engine and cause an overrich condition which mayresult in the engine stalling. Other times, during the open throttlecondition, this puddling will occur and a quick shut down to idle maycause a choking of the engine with an overrich mixture.

Under other circumstances, during idle running conditions, the puddleswill accumulate in these pockets and when the engine changes position,as in the case of chain saws, for example, which are shifted to manypositions, the accumulated fuel will dump into the engine and kill it.

It has been found that the openings provided as indicated above willsolve this problem. The size of the openings will be dependent on thesize of the engine and can be readily calibrated by personsknowledgeable in the art for different size engines. For example, for anengine with a Bk-cubic inch capacity two-cycle, two holes having adimension 0.052 inch were found to be suflicient. It is desirable thatthe holes be as small as possible to sweep the area clean since thelarger the holes, the more possibility there is of a loss of power. Anyreasonable sized hole will improve the conditions but a carefulcalibration will result in optimum operating efficiency. If a particularengine is intended to be used in a certain position, the holes can beintroduced into the sides wherein there is most likelihood of the fuelaccumulation.

Another advantage of the invention has been found in that an engine withthe present invention incorporated therein can idle with a largerthrottle opening so that tolerances between the throttle valve and themixing passage can be reduced and thus the overall expense ofmanufacture is less. Thus, it can be said that the invention eliminatesthe idle puddling; it eliminates full throttle puddling; it provides abetter comedown, that is, changing of speed from high open throttle toidle without the danger of flooding; it allows greater tolerances in thethrottle valve fit.

What is claimed as new is as follows:

1. In an engine and carburetor combination wherein fuel and air mixtureis introduced through a unidirectional valve, that improvement whichcomprises a unidirectional valve interposed between the mixing passageof the carburetor and the fuel passage of a crankcase housing of theengine, and means providing a plurality of fuel-air passagesuncontrolled by said valve leading from the mixing passage of thecarburetor to space in said fuel passage of the crankcase housingsurrounding and outside said valve to sweep any accumulated liquid fuelinto the crankcase housing.

1. In an engine and carburetor combination wherein fuel and air mixtureis introduced through a unidirectional valve, that improvement whichcomprises a unidirectional valve interposed between the mixing passageof the carburetor and the fuel passage of a crankcase housing of theengine, and means providing a plurality of fuel-air passagesuncontrolled by said valve leading from the mixing passage of thecarburetor to space in said fuel passage of the crankcase housingsurrounding and outside said valve to sweep any accumulated liquid fuelinto the crankcase housing.